LQWT10

LQWT, Field Team 2010

The second field season of the Late Quaternary Human Evolution in West Turkana Project built on the findings made in 2009 and of the West Turkana Field Survey (WTFS) organised by Richard Leakey earlier in the year. The work expanded the area being surveyed for fossil and archaeological remains both to the East and West of Natome, leading to the preliminary description of four new localities. The overall aims were to continue the reconstruction of the geomorphological history of the area in relation to the chronology of the changing levels of the lake in the past, as well as to survey for archaeological artefacts and animal and hominin fossil remains.

The work during the 2010 field season focused on a relatively small area (Kalakoel) to the west of the locality of Natome (surveyed in 2009), as well as preliminary surveys of two other localities identified during the WTFS (Nakwapo, Locher Akwan), with the specific objectives of:

carrying out a focused palaeontological and archaeological survey of a small area to the west of the locality of Natome, surveyed in 2009, where fossiliferous sediments were identified by Nyete Cyprian Mbevu and Robert Moru during the WTFS organised by Richard Leakey;

excavating a small number of trenches at the edge of local hills to establish local stratigraphic patterns and to collect samples for environmental and chronological analyses;

establishing the extent of the early Holocene high lake-level stand in this area.

The locality of Natome was extensively surveyed in 2009 (LQWT09). That survey also mapped some of the main palaeo-lake shorelines in the vicinity, marked by the presence of extensive shell layers both on the surface and in stratigraphic context. A GIS-based reconstruction of the highest probable lake stand in the late Pleistocene/early Holocene (at ~430 m) clearly shows that the locality of Natome sits at the edge of this high lake maximum extent, and thus marks the position of the last ancient beach. This is an important aspect of the interpretation of the remains recorded in 2009, which include a significant number of fish, crocodiles, turtles and hippopotami.

View of Nakwapo from the South, with shell layer visible in the exposed stratigraphy of the eroded hill slopes. Photo MM Lahr, 2010.

The 2010 survey focused on three new localities identified by Richard Leakey’s West Turkana Field Survey (WTFS), as well as a brief survey at the southern end of Natome. The new localities were named in consultation with local Turkana as Kalakoel, Nakwapo and Locher Akwan. These four rich localities are separated from each other by a short distance of between 5 and 10 km, two bridging the palaeolake shorelines (Natome and Kalakoel), and two that would have been underwater during the late Pleistocene/early Holocene highest lake-level stand, although exposed as the waters receded. As in 2009, survey was based on recording palaeontological and archaeological surface finds through a GPS and/or Total Station, complemented by targeted small-scale trench excavations to establish local stratigraphic patterns. With two exceptions, all the material recorded was deflated on the surface of eroded lake margin sediments, several of which in articulated anatomical positions indicating minimal horizontal movement. The latter was particularly the case on the surface of hill slopes in Locher Akwan 1 and Kalakoel 1. As is the case for Natome, the landscape to the west is ‘badlands’ – highly dissected sediments of lacustrine/fluvial nature, presumably later Quaternary in age, forming irregular hills of different heights. However, the locality of Kalakoel strides the landscape change from eroded naked hills to flat grass-covered plain, marking the edges of the last lake rise.

Initial phase of excavation of human cranium at KL1

The work focused first on the new locality of Kalakoel, in particular KL1, where the WTFS identified what appeared to be a partially buried fragmentary human cranium. A small excavation was put in place around the cranium, covering an area of 4 x 3 m. The area was excavated and sieved to a depth of 20 cm, when a sterile layer was met; the gullies draining the small rise where the cranium was found were brushed and sieved, resulting in a small number of fitting fragments being found in the sieve down a small gully to the NW of the find. The cranium itself consists of a partially fossilised, thick vault, slightly distorted post-mortem, with no facial skeleton. Also in situ at Kalakoel, a broken distal ulna was found with its second half still buried in sediment. A small excavation around it revealed finely laminated underlying sediments, but no further human or animal remains.

As with Natome, the locality of Kalakoel, which also strides the edge of the palaeolake sediments, proved to be rich in surface finds. The fauna identified consists mainly of fish, hippo and crocodiles, confirming the interpretation of a lake edge environment. Other remains include birds, bovids of all sizes, carnivores (including hyaena), elephants, equids, suids, ostriches andturtles. The locality may thus be described as a series of eroding hills, covered by low desert grasses and shrubs towards the W-SW, and scoured towards the E-NE, where hill slope onto a flat basin surface interrupted by individual steeply eroded hills. Layers of gastropod shells are visible near the top of the sedimentary sequence.

Aerial view of the northern face of Nakwapo, 2010. Photo by MM Lahr

The locality of Nakwapo is geomorphologically different in being much more discretely defined by a set of gently sloping hills from South to North, which end abruptly in a steep cliff of approximately 10 m height, marking a distinctive altitudinal shift between the locality and the relatively flat plain to the North. This lower northern surrounding plain clearly marks some geo-morphological boundary over some 2 km. This northern ‘cliff’ face exposes a distinctive, almost silicified, orange sandstone layer at its base, the broken-up remains of which are visible over the surface of the plain. The presence of orange-stained fossils on the surface to the north would suggest that these eroded from this sedimentary layer before deflation. A small trench at the lower edge of the hill, however, did not disclose any palaeontological remains in situ, which may nevertheless be found through more extensive excavation. At the top of the Nakwapo hills, layers of gastropod shells are visible, while faunal remains of similar appearance to those from Kalakoel and Natome lie on the eroded and deflated surfaces. Amongst these, a mineralised partial human mandible was found by Robert Moru. The fauna from the top deflated surface of Nakwapo also has a similar taxonomic range as the other localities surveyed, while that found on the surface of the surrounding plains and the low eroding hills to the East differ in the larger number of giraffes found.

The locality of Locher Akwan, just to the East of the road to Kangarisa, consists of a series of low-lying very eroded hills, cut-through by numerous gullies and channels. The surface of these is sandy silt, while the hill flanks and slopes are covered by small gravel mixed with organic remains and which in places forms a thick layer rich in fossil fish and occasionally other taxa. Among the latter, a number of fossils were found, consisting mainly of hippopotami, some crocodiles and small to medium size bovids. Other animal remains include buffalo, carnivores, large bovids, suids, elephant, turtle, and baboon. The presence of pottery in localised patches indicates also a very recent use of the area, consistent with the occasional find (completely absent elsewhere) of domesticates (cattle, goats, pigs and dog). A number of human remains of very different states of preservation and mineralisation were also found at the site.

Summary

The 2010 season of fieldwork was extremely successful, largely due to the amount and quality of information gathered by the field survey organised by Dr Richard Leakey and carried out by Nyete Cyprian and Robert Moru. That information served as the foundation for extending the survey of Natome into new localities in the vicinity, as well as to focus the effort of what was a comparatively short campaign. The work carried out confirmed a number of observations from previous years. First, that most of the fossiliferous sediments seen at Natome extends, discontinuously, to other areas that lied at some point at the edge of the high lake PalaeoTurkana. The fauna at these localities is consistent with this landscape, and clearly points to a lake-edge/swamp environment. Many of the sediments clearly relate to the last high stand of the lake, in the late Pleistocene/early Holocene, and most of the human remains found, as well as the artefacts and numerous bone harpoons, are consistent with this interpretation. These finds characterise an early Holocene population with a subsistence strategy that involved the intense exploitation of the lacustrine edge environment. Second, that aeolian and lake-recession processes have also exposed earlier sediments, probably deposited during previous lake high stands. This is consistent with the archaeological remains found, which include Middle Stone Age scatters. Finally, that although most of the human remains (and indeed the fauna) represent deflated and patinated fossils which have been exposed at the surface for a long period of time, some material is only eroding out of sediments in the very recent past, and has thus the potential for greater skeletal representation as well as offering depositional information. This was evident in the retrieval of a number of refitting pieces at Natome of remains first found in 2009.